Re: duct - fiberglass vs metal?
There are advantages to both.
Fiberglass is faster and easier to install. It's actually a flexible plastic duct with a fiberglass insulation wrap. The insulation means that less thermal loss/gain occurs to the air inside the duct in relation to the space the duct is located. Being that it's flexible, it is easier to route around obstacles. The major disadvantage is that it is susceptible to rodent damage.
Metal ducting is resistant to rodent damage, but suffers more thermal loss/gain, even when insulated. It's more expensive and time consuming to install.
There are probably more pro's/con's to each, these are the biggies that I can think of.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!